A recent increased demand for large-size, high-density, high-accuracy and high-reliability display devices has brought about the development of various pattern processing techniques. These various techniques are being used in fabricating plasma display panels (hereinafter, referred to as “PDPs”).
In recent years, to manufacture high-accuracy electrode circuits suitable for large-size display devices, photolithography employing a photosensitive conductive paste was developed. Photolithography is a method for fabricating a patterned electrode, which comprises printing a photosensitive conductive paste over the entire surface of a glass substrate, drying the substrate, exposing the substrate to an ultraviolet exposure system equipped with a photomask, developing an uncured region of the substrate shielded by the photomask with a developing solution and baking the remaining cured film at a predetermined temperature.
Korean Patent Laid-open No. 10-2005-122498 suggests preparation of a photosensitive phase composition using a conductive powder, an inorganic binder and an organic vehicle.
As mentioned above, in conventional cases, in an attempt to improve important parameters of electrodes i.e., resistance, sanding resistance of terminals and withstand-voltage characteristics, a conductive powder and an inorganic binder were added to a photosensitive paste.
However, the conventional method suffers from the problem that electrode patterns are often abnormally formed according to a mix ratio of a conductive powder and an inorganic binder.
The reason for abnormal formation of the electrode patterns is as follows. First, after a developing process, the phenomenon in which electrode patterns have the shape of a reverse trapezoid, so-called “undercut” occurs.
As a result, during the final process, i.e., the baking process, the phenomenon in which electrode patterns are curled at edges thereof, referred to as “edge-curl,” occurs.
The edge-curl phenomenon causes deterioration in withstand-voltage characteristics, resulting in deterioration in lifespan and luminescence efficiency of PDP products. In addition, terminal electrodes may be damaged by a sanding process, thus disadvantageously making it impossible for a PDP screen to normally display an image.
To solve this disadvantage, research has been made on methods for preventing the undercut phenomenon. The methods are based on improvement in exposure sensitivity and developing conditions, but fail to obtain satisfactory results.
In addition, Korean Patent Laid-open No. 10-2005-0116431 discloses a method for preventing the edge-curl phenomenon by minimizing a thickness contraction ratio of electrode patterns during baking. However, there is a limitation to prevention of the edge-curl phenomenon by controlling thicknesses of electrode patterns.